Integrated light pipe for optical projection

ABSTRACT

An optical device includes a first plate having a first transparent region defining an exit face of the device, and a second plate having a second transparent region defining an entrance face of the device. At least one lens is formed over at least one of the first and second transparent regions. First and second planar reflectors are spaced apart and fixed between the first and second plates in mutually-parallel orientations diagonal to the first and second plates, thereby defining an optical path through the device from the entrance face, reflecting from the first and second reflectors, through the exit face and passing through the at least one refractive surface.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No. 14/852,563, filed Sep. 13, 2015.

FIELD OF THE INVENTION

The present invention relates generally to optical devices and methods for their manufacture, and particularly to miniaturized integrated optical devices.

BACKGROUND

Miniature optical projectors are used in a variety of applications. For example, such projectors may be used to cast a pattern of coded or structured light onto an object for purposes of 3D mapping (also known as depth mapping). In this regard, U.S. Patent Application Publication 2008/0240502 describes an illumination assembly in which a light source, such as a laser diode or LED, transilluminates a transparency with optical radiation so as to project a pattern onto the object. (The terms “optical” and “light” as used herein refer generally to any of visible, infrared, and ultraviolet radiation.) An image capture assembly captures an image of the pattern that is projected onto the object, and a processor processes the image so as to reconstruct a three-dimensional (3D) map of the object.

PCT International Publication WO 2008/120217 describes further aspects of the sorts of illumination assemblies that are shown in the above-mentioned US 2008/0240502. In one embodiment, the transparency comprises an array of micro-lenses arranged in a non-uniform pattern. The micro-lenses generate a corresponding pattern of focal spots, which is projected onto the object.

Optical projectors may, in some applications, project light through one or more diffractive optical elements (DOEs). For example, U.S. Patent Application Publication 2009/0185274 describes apparatus for projecting a pattern that includes two DOEs that are together configured to diffract an input beam so as to at least partially cover a surface. The combination of DOEs reduces the energy in the zero-order (undiffracted) beam. In one embodiment, the first DOE generates a pattern of multiple beams, and the second DOE serves as a pattern generator to form a diffraction pattern on each of the beams.

As another example, U.S. Pat. No. 9,091,413 describes photonics modules that include optoelectronic components and optical elements (refractive and/or patterned) in a single integrated package. According to the inventors, these modules can be produced in large quantities at low cost, while offering good optical quality and high reliability. They are useful as projectors of patterned light, for example in 3D mapping applications as described above, but they may also be used in various other applications that use optical projection and sensing, including free-space optical communications.

SUMMARY

Embodiments of the present invention that are described hereinbelow provide integrated optical devices with enhanced reliability and manufacturability.

There is therefore provided, in accordance with an embodiment of the present invention, an optical device, which includes a first plate having a first transparent region defining an exit face of the device and a second plate having a second transparent region defining an entrance face of the device. At least one lens is formed over at least one of the first and second transparent regions. First and second planar reflectors are spaced apart and fixed between the first and second plates in mutually-parallel orientations diagonal to the first and second plates, thereby defining an optical path through the device from the entrance face, reflecting from the first and second reflectors, through the exit face and passing through the at least one refractive surface.

In a disclosed embodiment, the at least one lens includes at least a first lens formed over the first transparent region and at least a second lens formed over the second transparent region. Additionally or alternatively, the at least one lens includes at least first and second lenses formed on opposing sides of at least one of the first and second plates. Further additionally or alternatively, the first and second plates and the first and second planar reflectors define a cavity that contains the optical path, and the device includes third and fourth plates, which are fixed to the first and second plates and the first and second planar reflectors on opposing sides of the device in an orientation perpendicular to the first and second plates and the planar reflectors so as to enclose the cavity.

In one embodiment, the device includes a patterning element and a first spacer, fixed between the patterning element and the first plate so as to hold the patterning element in proximity to the exit face, as well as a light source mounted on a substrate and a second spacer, fixed between the substrate and the second plate so as to hold the light source in proximity to the entrance face, so that light emitted from the light source passes through the device along the optical path and transilluminates the patterning element, thereby generating patterned light.

There is also provided, in accordance with an embodiment of the present invention, a method for producing an optical device. The method includes fixing together first and second planar reflectors in mutually-parallel orientations with a predefined spacing between the first and second planar reflectors. First and second plates are provided, having respective first and second transparent regions that respectively define exit and entrance faces of the device, with at least one lens formed over at least one of the first and second transparent regions. The first and second plates are fixed to the fixed-together planar reflectors in an orientation diagonal to the planar reflectors, so as to define an optical path through the device from the entrance face, reflecting from the first and second reflectors, through the exit face and passing through the at least one refractive surface.

In some embodiments, providing the first and second plates includes forming an array of lenses on a transparent substrate, and dicing the transparent substrate to produce at least one of the first and second plates with the at least one lens formed thereon. Typically, the array of lenses is formed by molding or replication on the transparent substrate. Additionally or alternatively, fixing together the first and second planar reflectors includes fixing together multiple pairs of the planar reflectors so as to define multiple optical devices having respective optical cavities, wherein fixing the first and second plates includes attaching the transparent plate to the multiple pairs of the planar reflectors so that the lenses in the array are respectively aligned with the optical cavities before dicing the transparent substrate.

In a disclosed embodiment, the method includes, before fixing together the first and second planar reflectors, polishing and applying a reflective coating to respective inner surfaces of the planar reflectors from which the optical path is to reflect within the device.

In some embodiments, the first and second plates and the first and second planar reflectors define a cavity that contains the optical path, and the method includes fixing third and fourth plates to the first and second plates and the first and second planar reflectors on opposing sides of the device in an orientation perpendicular to the first and second plates and the planar reflectors so as to enclose the cavity.

In a disclosed embodiment, fixing together the first and second planar reflectors includes bonding a pair of reflective sheets to opposing sides of spacers having a thickness equal to the predefined spacing, dicing the bonded reflective sheets and spacers along a first direction perpendicular to the spacers to produce a set of strips, arranging the set of strips side-by-side, bonding the third and fourth plates to opposing sides of the arranged set of the strips, dicing the set of the strips and the third and fourth plates that are bonded thereto along a second direction diagonal to the strips so as to produce multiple rows of diagonal cavities, and dicing apart the cavities in each of the multiple rows to produce the fixed-together planar reflectors. Typically, fixing the first and second plates to the fixed-together planar reflectors includes, before dicing apart the cavities, arranging the multiple rows of the diagonal cavities side by side, and bonding the first and second plates to opposing sides of the arranged multiple rows, with an array of lenses on at least one of the first and second plates aligned with the cavities, wherein dicing apart the cavities includes dicing apart the first and second plates and the aligned lenses together with the cavities to which they are fixed.

In some embodiments, the method includes fixing a patterning element in proximity to the exit face, and fixing a light source in proximity to the entrance face, so that light emitted from the light source passes through the device along the optical path and transilluminates the patterning element, thereby generating patterned light. Typically, fixing the patterning element includes fixing a first spacer between the first plate and the patterning element, and fixing the light source includes fixing a second spacer between the second plate and a substrate on which the light source is mounted.

The present invention will be more fully understood from the following detailed description of the embodiments thereof, taken together with the drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are schematic sectional views of an integrated light pipe, in accordance with an embodiment of the invention;

FIG. 2A is a schematic top view of a reflector assembly used in producing an integrated light pipe, in accordance with an embodiment of the invention;

FIG. 2B is a schematic side view of a reflector strip cut from the assembly of FIG. 2A, in accordance with an embodiment of the invention;

FIG. 3 is a schematic top view of a stack of reflector strips, in accordance with an embodiment of the invention;

FIG. 4 is a schematic top view of an array of light pipe strips, which are cut from the stack of reflector strips shown in FIG. 3, in accordance with an embodiment of the invention;

FIGS. 5A and 5B are schematic side and top views, respectively, of an array of lenses, in accordance with an embodiment of the invention;

FIGS. 6A and 6B are schematic side and top views, respectively, of an array of integrated telescopes, in accordance with an embodiment of the invention;

FIG. 7 is a schematic side view of an array of integrated telescopes, in accordance with another embodiment of the invention;

FIG. 8 is a schematic side view of an array of diffractive stacks, in accordance with an embodiment of the invention; and

FIG. 9 is a schematic side view of an integrated optical projector, in accordance with an embodiment of the invention. 

1. An optical device, comprising: a first plate having a first transparent region defining an exit face of the device; a second plate having a second transparent region defining an entrance face of the device; at least one lens formed over at least one of the first and second transparent regions; and first and second planar reflectors, spaced apart and fixed between the first and second plates in mutually-parallel orientations diagonal to the first and second plates, thereby defining an optical path through the device from the entrance face, reflecting from the first and second reflectors, through the exit face and passing through the at least one refractive surface.
 2. The device according to claim 1, wherein the at least one lens comprises at least a first lens formed over the first transparent region and at least a second lens formed over the second transparent region.
 3. The device according to claim 1, wherein the at least one lens comprises at least first and second lenses formed on opposing sides of at least one of the first and second plates.
 4. The device according to claim 1, wherein the first and second plates and the first and second planar reflectors define a cavity that contains the optical path, and wherein the device comprises third and fourth plates, which are fixed to the first and second plates and the first and second planar reflectors on opposing sides of the device in an orientation perpendicular to the first and second plates and the planar reflectors so as to enclose the cavity.
 5. The device according to claim 1, and comprising: a patterning element; a first spacer, fixed between the patterning element and the first plate so as to hold the patterning element in proximity to the exit face; a light source mounted on a substrate; and a second spacer, fixed between the substrate and the second plate so as to hold the light source in proximity to the entrance face, so that light emitted from the light source passes through the device along the optical path and transilluminates the patterning element, thereby generating patterned light.
 6. A method for producing an optical device, the method comprising: fixing together first and second planar reflectors in mutually-parallel orientations with a predefined spacing between the first and second planar reflectors; providing first and second plates having respective first and second transparent regions that respectively define exit and entrance faces of the device, with at least one lens formed over at least one of the first and second transparent regions; and fixing the first and second plates to the fixed-together planar reflectors in an orientation diagonal to the planar reflectors, so as to define an optical path through the device from the entrance face, reflecting from the first and second reflectors, through the exit face and passing through the at least one refractive surface.
 7. The method according to claim 6, wherein the at least one lens comprises at least a first lens formed over the first transparent region and at least a second lens formed over the second transparent region.
 8. The method according to claim 6, wherein the at least one lens comprises at least first and second lenses formed on opposing sides of at least one of the first and second plates.
 9. The method according to claim 6, wherein providing the first and second plates comprises forming an array of lenses on a transparent substrate, and dicing the transparent substrate to produce at least one of the first and second plates with the at least one lens formed thereon.
 10. The method according to claim 9, wherein the array of lenses is formed by molding or replication on the transparent substrate.
 11. The method according to claim 9, wherein fixing together the first and second planar reflectors comprises fixing together multiple pairs of the planar reflectors so as to define multiple optical devices having respective optical cavities, and wherein fixing the first and second plates comprises attaching the transparent plate to the multiple pairs of the planar reflectors so that the lenses in the array are respectively aligned with the optical cavities before dicing the transparent substrate.
 12. The method according to claim 6, and comprising, before fixing together the first and second planar reflectors, polishing and applying a reflective coating to respective inner surfaces of the planar reflectors from which the optical path is to reflect within the device.
 13. The method according to claim 6, wherein the first and second plates and the first and second planar reflectors define a cavity that contains the optical path, and wherein the method comprises fixing third and fourth plates to the first and second plates and the first and second planar reflectors on opposing sides of the device in an orientation perpendicular to the first and second plates and the planar reflectors so as to enclose the cavity.
 14. The method according to claim 13, wherein fixing together the first and second planar reflectors comprises: bonding a pair of reflective sheets to opposing sides of spacers having a thickness equal to the predefined spacing; dicing the bonded reflective sheets and spacers along a first direction perpendicular to the spacers to produce a set of strips; arranging the set of strips side-by-side; bonding the third and fourth plates to opposing sides of the arranged set of the strips; dicing the set of the strips and the third and fourth plates that are bonded thereto along a second direction diagonal to the strips so as to produce multiple rows of diagonal cavities; and dicing apart the cavities in each of the multiple rows to produce the fixed-together planar reflectors.
 15. The method according to claim 14, wherein fixing the first and second plates to the fixed-together planar reflectors comprises, before dicing apart the cavities: arranging the multiple rows of the diagonal cavities side by side; and bonding the first and second plates to opposing sides of the arranged multiple rows, with an array of lenses on at least one of the first and second plates aligned with the cavities, wherein dicing apart the cavities comprises dicing apart the first and second plates and the aligned lenses together with the cavities to which they are fixed.
 16. The method according to claim 6, and comprising: fixing a patterning element in proximity to the exit face; and fixing a light source in proximity to the entrance face, so that light emitted from the light source passes through the device along the optical path and transilluminates the patterning element, thereby generating patterned light.
 17. The method according to claim 16, wherein fixing the patterning element comprises fixing a first spacer between the first plate and the patterning element, and wherein fixing the light source comprises fixing a second spacer between the second plate and a substrate on which the light source is mounted. 